On Wed, Apr 23, 2014 at 2:13 PM, Albert Yiamakis <vkicefire@gmail.com> wrote:

Hello,

I am looking to make a class, whose definition I cannot touch, model a
Range concept. To that end I use method 2,

http://www.boost.org/doc/libs/1_55_0/libs/range/doc/html/range/reference/extending/method_2.html

However, I am unable to specialize the relevant metafunctions
(range_const_iterator, range_mutable_iterator, range_iterator) since
they do not have an additional template parameter that would permit me
to employ enable_if.

Generally it isn't necessary to use enable_if to achieve this. There support for MFC containers was added by using method 2 to non-intrusively add support.

I have found this impossible without touching either the class'
definition or the metafunctions. Perhaps there is some other trick I am
not aware of, in which case I would greatly appreciate hearing about it.

I'm not sure if there is something special about your use-case that stops method 2 from working. Perhaps you could take a look at the MFC support in Boost.Range to see if this helps you add support for your classes.

If you can provide some code that shows the classes you are trying to make support ranges then I'd be happy to try and help.

If such a trick does not exist, then should these metafunctions feature
an additional template parameter? Given that this is one of the methods
to extend the library, it would make sense that one wishes to do so on
conditions that enable_if can check.

So far I have never needed an additional parameter. I suspect that we don't need the additional parameter, but I'm willing to look at new use cases and make appropriate changes if they are warranted.

Albert

Regards,

Neil Groves